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bkballa SEFI Member
Joined: 29 Nov 2010 Posts: 11
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Posted: Sun Mar 06, 2011 1:27 pm Post subject: Design of Post-tensioned Prestressed Box Girder Bridge |
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Dear sefians,
I am new to sefindia.org. This is my first post in the forum. I have been designing mostly RCC T-beam bridges for sometime. For the current project I am working on required a use of >50 m span. By doing cost analysis, PSC box girder is deemed more economical than Steel Truss. Someone else designed the 52.5m PSC Box Girder with total depth of 3.5 m.
Coming to my question. I want to design PSC or RCC Box Girder in my own. How do I start. How do I select initial sections. How much prestressing cables do I select.
I tried to model the simply supported 52.5m Box Girder on SAP2000 v14 with all the prestressing cables. The BM profile due to DL is "negative at support"; BM due to prestress is zero throughout. Did I miss something on modeling the Box Girder?
Thanks.
Biswa Balla
Bridge Design Engineer |
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B.V.Harsoda General Sponsor
Joined: 19 Jan 2009 Posts: 2329 Location: RAJKOT,GUJARAT, INDIA
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Posted: Thu Aug 09, 2012 5:38 am Post subject: |
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Refer below Link:-
http://www.sefindia.org/forum/viewtopic.php?p=50225#50225 |
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kamal SEFI Member
Joined: 08 May 2010 Posts: 10 Location: MUMBAI
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Posted: Tue Mar 26, 2013 4:41 am Post subject: |
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hi biswa,
as you mentioned that u are getting negative moment at support , that is true you are not doing anything wrong.
in posttensioned girders generally initial 2 m solid portion is called diaphragm , & u will get tension in this protion as the prestressing has reverse effect in this part. so this part is designed as reinforced not prestressed.
To start with the design u can take the depth = span/12 to span/15 , select web & bottom slab thickness with requirement of sufficient cover to prestressing cables. |
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